The Regener-Pfotzer (RP) maximum is the altitude at which cosmic radiation intensity is the greatest. A decrease of the altitude of the interaction layer, assumed to be measured by the RP maximum, has been suggested to account for a reduction in the secondary cosmic ray flux measured at the surface of the Earth during a total solar eclipse. To investigate this suggestion, high altitude cosmic radiation was measured using Geiger Mueller (GM) counters carried beneath weather balloons both before and during the total solar eclipse on 21 August 2017. The 19 and 20 August 2017 omnidirectional RP maxima occurred at an average altitude of 20.2 km ± 0.9 km. During the eclipse of 21 August 2017 the omnidirectional RP maxima occurred at an altitude of 20.4 km ± 0.8 km. The 19 and 20 August 2017 vertical coincidence RP maxima occurred at an altitude of 18.3 km ± 1.0 km. During the eclipse the vertical coincidence RP maxima occurred at 18.0 km ± 1.0 km. Our results do not show any decrease in the altitude of either the omnidirectional or the vertical coincidence RP maximum outside the range of our measurements before the eclipse.

Cosmic ray air showers result when high-energy particles from outer space strike atmospheric nuclei and produce downward sprays of secondary rays including electrons, positrons, muons and neutrinos. The charged particles in such cosmic ray showers can trigger Geiger counters as they pass through the detectors. Hence monitoring coincidences between two or more Geiger counters can provide insight into the direction of travel and/or the physical spatial extent of a cosmic ray shower. We present a preliminary report on a stratospheric ballooning payload designed to make coincidence measurements of charged particles traveling at zenith angles of 0 degrees (vertical) and 90 degrees (horizontal). This was a follow-on to an earlier experiment in which we used a stepper motor to repeatedly change the angle (with respect to zenith) of a pair of coincidence-counting Geiger counters during a stratospheric balloon flight. The new payload contains four fixed pancake-shaped RM-80 Geiger counters -two stacked vertically (aligned with zenith) and two stacked horizontally (aligned perpendicular to zenith). Each pair of detectors is separated by 18 cm, so as to narrow the opening angle of the coincidence detector. This configuration can sample both vertical and horizontal coincidences simultaneously, with no moving parts as was done with the stepper motor. Although the new configuration cannot study coincidences at intermediate angles, it also allows us to study triple and quadruple coincidences.

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